The information requested is not currently held.
The Home Office, Ministry of Justice and Attorney-General's Office are currently working with the National Coordinator for Terrorist Investigations to improve the quality of data on arrests and convictions under terrorist legislation and other related legislation. As soon as this is complete a statistical bulletin to cover information on arrests and convictions will be published, but as yet we do not have a confirmed date.
The bulletin will say how many individuals have been charged and convicted for encouragement of terrorism; however it will not break it down any further.